Setting of rivet elements is generally known. A method for setting of rivet elements with a riveting tool driven by an electric motor is known from DE 10 2005 054 048 A1. The quality of the setting process is monitored by means of the electric current consumed by the electric motor of the riveting tool. The quality of the setting process is then viewed as acceptable, if the maximum current consumed by the electric motor during the setting process lies within a stipulated value range. A shortcoming in this method is that the quality of the setting process of the riveting tool is only evaluated by means of the maximum consumed current. This permits only a retrospective view of the setting process. The rivet process is conducted to the end in this method. Consequently, it cannot be evaluated at which location of the setting process the setting process was conducted incorrectly. It can therefore happen that the maximum consumed current lies within the stipulated value range. However, it cannot be recognized that an error occurred in the setting process before or after reaching the maximum consumed current. However, if the rivet was pulled too quickly or too slowly at a location during the setting process, this cannot be established.
A method for setting of blind rivets and blind rivet nuts is known from DE 43 39 117 A1, in which a tensile force is generated with an electric motor during a setting process. A setting device for blind rivets and blind rivet nuts with a tension mechanism driven by an electric motor is also known. In this method, the input current of the electric motor is monitored, in which case the consumed current is a direct gauge of the torque taken up by the electric motor. The tensile force of the setting device of the setter can be determined via the torque. The tensile force permits a conclusion concerning the quality of the rivet joint. Thus, the current trend can be used subsequently as a criterion for evaluating the setting process. In the method disclosed in DE 43 39 117 A1, it is monitored whether the consumed current of the electric motor reaches a maximum value during the setting process. If the maximum value is not so large that it falls within a stipulated target current range, this is a sign of defective riveting or an error in the setting device. If the maximum value is too large, this can be attributed to increased friction in the setting device, which is caused by soiling, or caused by choosing an incorrect rivet. A shortcoming in this method is that, here again, an evaluation of the setting process is made possible only subsequently. A setting process is then evaluated as acceptable, if the maximum value of the consumed current lies within the target current range. This means that setting processes are accepted, although perhaps before or after reaching the maximum value, the rivet element was pulled incorrectly. The maximum value can lie within the target current range, but the setting process can nevertheless be defective.
It is known from EP 0 454 890 A1 to provide a force measurement device in setting devices in the form of a strain gauge or pressure capsule. A shortcoming in such force measurement devices is that they represent additional components that involve additional cabling and wiring expense. Evaluation of the setting process is also conducted here only afterward by comparison with target values stored in a memory.